The following description relates to one or more processors for an electronic endoscope that are connectable with plural types of videoscopes each of which is replaceable relative to the processor and provided with a color adjustment processing device.
An electronic endoscope has been known, which is configured to observe an intended region inside a body with a solid state image sensor inserted into the body such as a charge coupled device (CCD) image sensor. A conventional electronic endoscope includes a cable-shaped videoscope configured to be inserted into the body, and a processor configured to supply, to the videoscope, light for illuminating the observed region inside the body and to convert an image signal received from the videoscope into a video signal through various sorts of processing. Further, the conventional electronic endoscope includes a monitor configured to display thereon an observed image based on the video signal generated by the processor. The processor has a light source configured to emit light for illuminating the observed region. The light emitted from the light source is transmitted to the distal end of the scope through a light guide (an optical fiber bundle) provided within the videoscope. When the observed region is illuminated with the light emitted from the distal end of the scope, the light is partially reflected to form an image of the observed region on the image sensor disposed at the distal end of the scope. Then, an image signal corresponding to the image of the observed region is read out from the image sensor.
The videoscope is detachably attached to the processor. Thereby, it is possible to use a desired one of various types of videoscopes depending on the observed region or the body size of the examined subject. In other words, plural types of videoscopes can be utilized in a manner replaceable relative to a single processor. Further, each of the plural types of videoscopes is connectable with two or more processors with different capabilities and different performances.
In the meantime, the design (e.g., a viewing angle, an observation depth, an absorption spectrum, etc.) of each optical element such as a lens and a color filter may vary depending on the type of the videoscope. Therefore, even though the same processor is used, how the image displayed on the monitor is visually sensed (e.g., in terms of brightness or color tone) may vary depending on the type of the videoscope connected to the processor. Moreover, depending on the type of the light source used, the color tone of the observed image varies due to the emission spectrum that varies depending on the type of the light source. For example, a xenon lamp, which is the most commonly used as a light source for an endoscope, emits white light with spectral characteristics close to those of the daylight color. On the other hand, a halogen lamp emits yellowish light with few short wavelength components. Thus, owing to the emission spectrum varying depending on the light source used, even though the same videoscope is used to take an image of the same region, the color components of the color image signal read out from the image sensor vary depending on the type of the light source used.
Japanese Patent Provisional Publication No. 2002-369798 (hereinafter, simply referred to as '798 Publication) discloses a solution to achieve highly faithful color reproducibility by compensating the color tone differences between the observed images generated by different types of videoscopes or by different types of processors (light sources). According to an electronic endoscope system disclosed in '798 Publication, a storage provided within a videoscope previously stores thereon data on the characteristics of the videoscope and color adjustment data adapted to each of plural types of light sources. Based on the data stored, a color adjustment process adapted to the videoscope and light source to be used is performed by an initial signal adjustment circuit loaded in the videoscope. Namely, the electronic endoscope system disclosed in '798 Publication can display observed images with the same color tone on the monitor, regardless of the typed of videoscope used, by compensating at the videoscope side the difference between color tones caused due to different types of videoscopes or light sources. In the same manner, no matter what type of processor (light source) is used, it is possible to display observed images with the same color tone on the monitor and thus to improve the color reproducibility.